From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1035252AbdAJCX6 (ORCPT ); Mon, 9 Jan 2017 21:23:58 -0500 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:38779 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1030531AbdAJCXu (ORCPT ); Mon, 9 Jan 2017 21:23:50 -0500 Date: Mon, 9 Jan 2017 18:23:38 -0800 From: "Paul E. McKenney" To: "Rafael J. Wysocki" Cc: Borislav Petkov , "Zheng, Lv" , "Wysocki, Rafael J" , "Moore, Robert" , J?rg R?del , lkml , Linux ACPI Subject: Re: 174cc7187e6f ACPICA: Tables: Back port acpi_get_table_with_size() and early_acpi_os_unmap_memory() from Linux kernel Reply-To: paulmck@linux.vnet.ibm.com References: <20170108130355.vxhjmj6dlkqw6hyq@pd.tnic> <1AE640813FDE7649BE1B193DEA596E886CE27B7E@SHSMSX101.ccr.corp.intel.com> <1AE640813FDE7649BE1B193DEA596E886CE27BEE@SHSMSX101.ccr.corp.intel.com> <20170109093329.jd7uwlcpci4icpd3@pd.tnic> <20170109221831.GC3800@linux.vnet.ibm.com> <20170109231501.xrhwsv46mznw3kqt@pd.tnic> <20170109233204.GG3800@linux.vnet.ibm.com> <20170109234039.mfefmv5dv4shxnfn@pd.tnic> <20170109235211.yetponvbexvalkir@pd.tnic> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-GCONF: 00 X-Content-Scanned: Fidelis XPS MAILER x-cbid: 17011002-0008-0000-0000-00000684BE17 X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00006405; HX=3.00000240; KW=3.00000007; PH=3.00000004; SC=3.00000199; SDB=6.00805275; UDB=6.00391913; IPR=6.00582896; BA=6.00005038; NDR=6.00000001; ZLA=6.00000005; ZF=6.00000009; ZB=6.00000000; ZP=6.00000000; ZH=6.00000000; ZU=6.00000002; MB=3.00013872; XFM=3.00000011; UTC=2017-01-10 02:23:42 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 17011002-0009-0000-0000-00003E809FC0 Message-Id: <20170110022338.GJ3800@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2017-01-10_01:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 suspectscore=1 malwarescore=0 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1612050000 definitions=main-1701100029 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jan 10, 2017 at 02:27:16AM +0100, Rafael J. Wysocki wrote: > On Tue, Jan 10, 2017 at 12:52 AM, Borislav Petkov wrote: > > On Tue, Jan 10, 2017 at 12:40:39AM +0100, Borislav Petkov wrote: > >> Lemme run it. > > > > Well, it boots but I get: > > > > [ 0.291447] ------------[ cut here ]------------ > > [ 0.291702] WARNING: CPU: 0 PID: 1 at kernel/rcu/tree.c:3993 rcu_scheduler_starting+0x5c/0x70 > > [ 0.292107] Modules linked in: > > [ 0.292277] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.10.0-rc3+ #21 > > [ 0.292540] Hardware name: HP HP EliteBook 745 G3/807E, BIOS N73 Ver. 01.08 01/28/2016 > > [ 0.292893] Call Trace: > > [ 0.293072] ? dump_stack+0x46/0x63 > > [ 0.293285] ? __warn+0xec/0x110 > > [ 0.293487] ? rcu_scheduler_starting+0x5c/0x70 > > [ 0.293735] ? kernel_init_freeable+0x58/0x19a > > [ 0.293976] ? rest_init+0x80/0x80 > > [ 0.294153] ? kernel_init+0xa/0x100 > > [ 0.294334] ? ret_from_fork+0x22/0x30 > > [ 0.294525] ---[ end trace 4c0fe009ed4dc740 ]--- > > > > TBH, I like Rafael's suggestion in the other mail to stick with fixing > > this in ACPI, especially this is an ACPI problem, not RCU. Well, > > more or less: RCU could be taught to *not* do schedule_work() if > > workqueue_init() hasn't happened yet but that's a tangential. > > > > So, I'm going to bed. When I wake up, I want to see working fixes! > > > > :-))) > > Well, if the https://patchwork.kernel.org/patch/9504277/ patch from Lv > worked, the attached one should work too (please test), but it can be > justified in a slightly more convincing way. > > Namely, the idea is that acpi_os_read/write_memory() should never be > used before invoking acpi_os_initialize() and since those are the only > places where the list of memory regions is walked under RCU without > extra locking, it is safe to skip the RCU synchronization until that > happens. > > Thanks, > Rafael Makes sense to me! It looks like I can make the grace-period-free boot-time window for CONFIG_PREEMPT=y kernels quite a bit narrower, but it does not look like something suitable for jamming into 4.10. Thanx, Paul > --- > drivers/acpi/osl.c | 8 +++++++- > 1 file changed, 7 insertions(+), 1 deletion(-) > > Index: linux-pm/drivers/acpi/osl.c > =================================================================== > --- linux-pm.orig/drivers/acpi/osl.c > +++ linux-pm/drivers/acpi/osl.c > @@ -378,7 +378,9 @@ static void acpi_os_drop_map_ref(struct > static void acpi_os_map_cleanup(struct acpi_ioremap *map) > { > if (!map->refcount) { > - synchronize_rcu_expedited(); > + if (acpi_os_initialized) > + synchronize_rcu_expedited(); > + > acpi_unmap(map->phys, map->virt); > kfree(map); > } > @@ -671,6 +673,8 @@ acpi_os_read_memory(acpi_physical_addres > bool unmap = false; > u64 dummy; > > + WARN_ON_ONCE(!acpi_os_initialized); > + > rcu_read_lock(); > virt_addr = acpi_map_vaddr_lookup(phys_addr, size); > if (!virt_addr) { > @@ -716,6 +720,8 @@ acpi_os_write_memory(acpi_physical_addre > unsigned int size = width / 8; > bool unmap = false; > > + WARN_ON_ONCE(!acpi_os_initialized); > + > rcu_read_lock(); > virt_addr = acpi_map_vaddr_lookup(phys_addr, size); > if (!virt_addr) {